I agree with Philip regarding all the possibilities he lists.

However, my experience in childhood in the Forest was that there was entrenchment within denominations, so that transfers or defections were rare and greatly to be disapproved. My grandparents at Lydney were staunch Methodists, but if you called them Wesleyan Methodists you were liable to fire and brimstone, since they were of the old pre-1933 Primitive Methodists. In Lydney, Springfield was the old "Prim" chapel whereas the Wesleyans were at Hill Street. The twain weren't often liable to meet. And if I had ever suggested to my grandparents that we should go to the Anglican parish church of St Mary, I would have been in deep trouble, since a church with bells and a clock was, to them, almost devilish.

The Bible Christians spoken of in this enquiry were founded around 1815 by a Wesleyan. Until a merger towards Methodist unity in 1907, they were an offshoot who began in Devon and Cornwall and went about with a brand of preaching that majored big time on wanting to eradicate of poverty and hypocrisy. This sometimes got them chucked out of their homes by the rich and hypocritical. The dates in question in this thread can fairly be described as coming in the wake of the 18th century Methodist revival when all manner of zeal and counter-zeal was afoot.

It's therefore reasonable to speculate that some Bible Christians in the Forest, converted by the powerful social message of their preachers, subsequently copped a measure of persecution that on reflection they felt they could reach heaven without, although I have no evidence of that having happened locally.

However, given that the Bible Christians merged with certain other Methodists in 1907, the return to the Church of England by 1909 mentioned in this thread just might have been caused by a feeling that if their favourite brand was being subsumed they might just as well go back to them there devilish clocks and bells!